In a semiconductor manufacturing process, a plasma processing apparatus has been widely used to perform a plasma processing for the purpose of deposition or etching of a thin film. Examples of the plasma processing apparatus include a plasma chemical vapor deposition (CVD) apparatus for performing a thin film deposition processing and a plasma etching apparatus for performing an etching processing.
In a recent plasma processing, a plasma processing apparatus using excitation of a processing gas by microwaves has been used in some cases. In the plasma processing apparatus, microwaves for plasma excitation generated by a microwave generator are radiated by using a slot plate having a plurality of slots formed therein. Further, in the plasma processing apparatus, the microwaves for plasma excitation radiated from the plurality of slots are introduced into a plasma processing space by a dielectric provided between the slot plate and the plasma processing space.
Incidentally, in such a plasma processing apparatus, it is effective to increase an electric field on the surface of the dielectric on the plasma processing space side in order to efficiently generate plasma. In this regard, a technique has been proposed in which a recessed portion recessed in a tapered shape is provided on the surface of the dielectric on the plasma processing space side, and an electric field corresponding to microwaves is converged by the recessed portion. See, for example, Japanese Patent Laid-Open Publication No. 2015-188061.